There is a demand in recent years on connectors to be adapted for two kinds of standards, such as a new standard and a conventional standard. Meeting the demand, such a connector has contacts arranged inside its body at their respective positions predefined according to each of the standards. A contact conforming to the conventional standard may be disposed offset toward one of contacts of a differential pair conforming to the new standard.
The presence of such offset contact causes reduction in capacitance and increases in impedance of the one of the paired contacts. This further causes an impedance mismatch between the differential pair contacts, which leads to degradation of transmission characteristics of the connector.
A known means to match impedances of such differential pair contacts is that a ground contact is provided at a middle and lower position of the paired contacts, such that each widthwise end of the ground contact overlap in plane position with a widthwise end of each of the paired contacts (see Patent Literature 1).    Patent Literature 1 Japanese Published Patent Publication No. 2003-505826, based on the international application published as WO/01/006602